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Multi-Way Conventional loudspeakers with crossovers

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Old 12th November 2013, 02:16 AM   #1
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Default Mentor Needed

I have custom designed speakers from 1979 that don't sound like they did originally and I'd like to restore them. Ordinarily I wouldn't consider doing this but these are extremely special speakers built for me in 1978 by an audiophile/electronic engineer genius.

These were designed by Dean L. Weeks. This is the man who designed boxes and crossovers with Ken Kreisel for his original M&K prototype subwoofers.

My pair are Deans 4th full range prototype, a sealed cabinet design. They are "4 ways" consisting of a 12" Phillips Driver with a 12" passive radiator, a 6" Isophon soft dome mid range, Isophon 4" hard dome tweeter and a 2.5" paper Phillips super tweeter. Dean passed away in 1992, and there are no records of his designs, although I am reaching out to his family in hopes we might find something helpful.

These speakers are truly amazing (by even the snootiest of audiophile standards) I am a Hollywood film and television professional of over 30 years. I'm looking for someone willing to advise me in the restoration of the speakers. My expertise in electronics is limited to being a plus-minus / resitance-capacitance / level tech who can solder somewhat adequately, so that's why I need a step by step mentor to get me through the process. Along the way, I will produce a video documenting the restoration, and release the film along with build plans to the audiophile community as a tribute to the man that designed these.

The drivers seem to be in good working condition, although I expect the values of electronic components in the crossovers have changed causing them to not sound as amazing.

If you are willing to mentor me through the process of evaluating the crossovers so I can replace each component systematically, please contact me. I would like to restore the entire crossover, but not change the design of the original speakers. Some components may have improved over the years, so I'm very excited about the potential this project presents.

I would be extremely grateful for your assistance.

All the best, Dale Dimmick
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Old 12th November 2013, 03:29 AM   #2
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Default Suggested First Steps ...

... to document what you have.
1) Specs for the drivers (when new):
2) Crossover Scamatic (including component values)
3) Enclosure Dimensions (acoustically important)
4) Based on this, model the system performance.
5) Measure what you have and compare.
6) Plan renovation required

Expect at a minimum, the crossover rebuild will require replacement of noisy L-pads and deteriorated capacitors.

Before you get started, determin what resources you will need to accomplished these initial steps.

Regards,

WHG
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Old 12th November 2013, 04:08 AM   #3
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Dale,

Why not post a few pics of the speakers?

Also, what do you feel is lacking or wrong with the speakers today?

What are the surrounds on the drivers?
Foam? Rubber? Paper? Paper with dope?

As far as measurement, the suggestion is a good one, if only to have a basis for comparison and to identify any glaring problems/issues.

Measurement software is available free, and measurement mics and preamps are not particularly expensive. Your laptop will be good enough to handle the input from the mic pre and run the software.

Just so you know, the state-of-the-art has come some distance since these drivers were new. Even so, these might sound very nice.

The obvious changes would be to replace any electrolytic caps with film caps, and any mylar/polyester caps with polypropylene. Also it is reasonable to consider changing the wirewound resistors for higher quality "film" resistors, like those made by Vishay and Caddock.

But you have to be careful as part of the "sound" may have come from the particular type of components used back then. More modern components may be better sounding, or may reveal some things better left hidden. Usually better components make speakers sound better.

The inductors need to be carefully considered before changes are made.
Are they air core, ferrite core, or iron core?
Did the designer use the DCR of the inductors as part of the design?
Newer low DCR air core inductors may skew the crossover as well as the pass band response. But you can compensate for this, once the original crossover's connections (schematic) is traced out and put on paper.

Fun, isn't it?

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Old 12th November 2013, 07:39 AM   #4
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Thanks guys. I'll move forward over the next few days. I don't have the skill to create a schematic, but I can open one up and photograph to give you a visual initially.

I do remember Dean talking about using military spec components and oil or maybe fluid filled caps. Sound familiar? And it seems like they were pretty large. Anyway, i'll post pics in a few days.
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Old 12th November 2013, 04:05 PM   #5
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Dale. Where are you located?
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Old 12th November 2013, 11:15 PM   #6
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Quote:
Originally Posted by DaleD Quads View Post
Thanks guys. I'll move forward over the next few days. I don't have the skill to create a schematic, but I can open one up and photograph to give you a visual initially.

I do remember Dean talking about using military spec components and oil or maybe fluid filled caps. Sound familiar? And it seems like they were pretty large. Anyway, i'll post pics in a few days.
I reused the Isophon speakers from a 1960's console stereo, they sound great. Some of the old designs will literally last a lifetime if not abused.
Resistors don't go bad unless they are burnt.

I have measured 50 year old oil-filled caps within a few % of the rating.
I have measured brand new capacitors that were 10% off.

Measure your capacitors with a tester, if they are within 10% of the value stated, don't mess with them, they were part of the original design.
"Improvements" often sound different, but may not be better.
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Old 13th November 2013, 07:25 AM   #7
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THanks, I'm cautious and suspicious about changing too much of the original design.
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Old 14th November 2013, 12:21 AM   #8
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i'd agree on the oil filled, they usually last forever... also they have a unique sound.

But, if you really want help via the internet, it would be best to answer the pertinent questions that were asked.

If you want help in person, then telling people your geographic location would help a lot.

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Old 14th November 2013, 02:50 AM   #9
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Default Physical Loation

As requested: I'm in Washington State, 1 hour north of Portland, Oregon.
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